System and method for delivering a fluid with a consistent total volumetric flowrate

ABSTRACT

Provided is a method for delivering a medical fluid. The method includes delivering a fluid volume, which includes contrast and/or a flush fluid, at a preselected total volumetric flowrate during a first duration of a fluid delivery procedure. The amount of the contrast agent and the flush fluid in the fluid volume can be controllably varied during the first duration of the fluid delivery procedure so as to substantially maintain a preselected total volumetric flowrate throughout the first duration of the fluid delivery procedure. Also provided is a fluid delivery system capable of performing this method.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 16/346,219filed Apr. 30, 2019, which is a § 371 national stage application ofInternational Patent Application No. PCT/US2017/062728, filed on Nov.21, 2017, which claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/425,312, filed Nov. 22, 2016, the entirecontents of which are hereby incorporated herein by reference. Thisapplication is related to International Patent Application No.PCT/US2017/062768, filed Nov. 21, 2017, which claims the benefit of U.S.Provisional Application Ser. No. 62/425,303, filed Nov. 22, 2016, theentire disclosure of which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

This disclosure is related to systems and methods for fluid delivery,and, particularly, to systems and methods for delivery of a fluid to apatient, such as delivery of a contrast agent to a patient during amedical injection and/or imaging procedure.

Description of Related Art

The following information is provided to assist the reader to understandthe invention disclosed herein and the environment in which it willtypically be used. The terms used herein are not intended to be limitedto any particular narrow interpretation unless clearly stated otherwisein this document. References set forth herein may facilitateunderstanding of the present invention or the background of the presentinvention. The disclosure of all references cited herein areincorporated by reference.

It is often desirable to use a contrast agent to enhance images of aregion of the body obtained through imaging procedures performed withscanning technologies such as, for example, computed tomography (CT),angiography, ultrasound, magnetic resonance imaging (MRI), nuclearmedicine, and molecular imaging. Typically, the contrast agent isinjected into a blood vessel of a patient and, once it flows to andreaches a desired concentration in the region of interest (ROI), theregion is scanned by the scanner according to the imaging procedureselected by the radiologist or other medical personnel. The resultingcontrast-enhanced images of the ROI can then be viewed on a displayassociated with the scanner itself or with another system such as apicture archiving and communication system (PACS) for purposes ofreaching a diagnosis for and/or providing treatment to the patient.

In some cases, to reduce the amount of contrast used, the contrast agentinjection is immediately followed by an injection of a flush fluid, suchas saline. This is commonly done to improve the efficiency of the use ofcontrast agent, either to save money or to reduce the effect of thecontrast agent on the patient's body or both. This saline injectionhelps to flush or wash the contrast agent out of the peripheral veinsand into the central circulation. This also helps reduce the creation ofartifacts that may be created by concentrated contrast agent in the armsbeing in the CT beam. A saline flush has been found especially usefulwhen small volumes of contrast agent are used, as in MRI.

In certain imaging procedures, it is also desirable to produce differentlevels of enhancement in two or more regions of the body or in differenttissues in the same region of the body. For example, in various cardiacimaging procedures, it is desirable to produce high contrast in thecoronary arteries and at the same time moderate contrast in the rightheart so that both the diameters of the arterial lumens and the motionof the heart wall can be visualized in one scan without artifacts causedby, for example, concentrated contrast streaming into the right heart.

To achieve this with an injection system with a single concentration ofcontrast and no saline flush capability, a first phase with a highcontrast delivery rate is initially injected (a given concentration at ahigh flowrate). The second or following phase has a reduced contrastdelivery rate (same concentration at a reduced flowrate). If theinjection system has a saline flush capability, there may be a thirdphase with a saline flush at the volumetric flowrate of either the firstor the second phase.

It is not generally realized that in injection procedures in which theflow of the contrast is slowed down in the second phase (in this casewith no saline), the flow of the fluid that has already been injectedand is downstream of the intravenous (IV) catheter tip also slows downbecause the flow in the veins is the sum of the native or naturalflowrate and the injected flowrate. This causes the shape of thecontrast bolus to change downstream of the injection site and thus as itarrives in the heart. For example, FIG. 7 provides example details onanatomical variations in the circulatory system of the human bodyinclusive of the exemplary changes in the diameter of vessels in thehuman body as they lead to and approach the human heart. FIG. 8 providesa rudimentary model of the flow of fluid through the venous system,illustrating how the larger “pipes” closer to the heart accommodateincreased flow. While an injected fluid flow added to the existing flowmay be high enough to significantly change the flow in some vessels, itmay not be enough to significantly change the flow in other vessels. Asflow rate decreases, the flow downstream changes nearly instantaneously,but nonlinearly due in part to the fact that the venous system iscomprised of “pipes” that can stretch or change volume depending on themagnitude of the flow. Consequently, in this prior art injection method,this changes the concentration of contrast in the blood at thatlocation, and it also reduces the quality and consistency of the imagestaken of that ROI as they are now dependent upon the native flow in thepatient's vessels and the vessel geometry.

In the OptiBolus™ Bolus Shaping Software offered by the Guerbet Group(formerly by Mallinckrodt), the method of contrast administrationinvolves an injection procedure that employs a truncated, exponentiallydecaying bolus profile in the first phase with or without use of asaline flush. FIG. 2A, for example, shows a normal Optibolus profile inthe first and only phase without the use of a saline flush. FIG. 3A,however, shows the OptiBolus profile in the first phase with the use ofa saline flush in the second phase at the flowrate equal to that of thecontrast at the end of the first or contrast phase. As discussed below,the OptiBolus profiles follow the models and injection protocolsdiscussed in U.S. Pat. Nos. 6,055,985 and 6,635,030, both to Bae et al.,the entire contents of each of which are incorporated herein byreference.

Similarly, in the approach developed by Fleischmann et al. (described inthe article “Mathematical Analysis of Arterial Enhancement andOptimization of Bolus Geometry for CT Angiography Using the DiscreteFourier Transform,” Journal of Computer Assisted Tomography, Volume23(3), May/June 1999, pp. 474-484), they employ a method that attemptsto determine an ideal bolus profile, as shown in FIG. 4A herein, usingthe response of the patient to a test bolus. Because of the limitationsinherent to injection systems, however, Fleischmann et al. approximatethat comparatively more complex ideal bolus profile with the “normalbolus profile” shown in FIG. 5A herein. This normal profile ismanifested as a relatively large magnitude rectangular bolus of contrastin the first phase of an injection procedure followed by a comparativelysmaller, long rectangular contrast bolus in the second phase of theprocedure.

In the Personalized Patient Protocol Technology (P3T®) softwarepioneered by Bayer, the method of administration employs a three-phaseinjection procedure as shown in FIG. 6 . A large normal rectangularcontrast bolus is carried out in the first phase followed by a secondphase, a phase of dual fluid flows, composed of a mix of contrast andsaline injected at the same total flow rate used in the first phase.This is followed by an all saline bolus in the third phase, again at thesame total flow rate to avoid the problem of the bolus being adverselyaffected downstream by a change in the injected flow rate. In each ofthe above referenced figures, the volume of contrast delivered isrepresented by the area “C” while the volume of flush fluid (e.g.,saline) delivered is represented by the area “F.”

Dual flow injection protocols involve the administration of differentcontrast concentrations at a reasonably consistent total volumetricflowrate. This may be achieved by injecting contrast and/or saline invarying ratios into a patient over the course of one or more phases ofinjection. For example, in a typical dual flow injection procedure, asshown in FIG. 6 , a contrast medium at full strength is injected duringa first phase of the procedure, an admixture of both contrast and salineis injected during a second phase, and then a third phase may beemployed in which only saline is injected as a means to push theinjected fluid as a bolus through the vasculature to the region(s) ofinterest. In the context of cardiac imaging, the reason multi-phase dualflow injections are used is to at least mitigate the left heart/rightheart imaging issue. To do so, it is important that the injectionprocedure will consistently result in the formation of a bolus that willenable the arrival and presence of contrast, in the appropriateconcentration and amount, in the desired vessel/ROIs at the same timethat the vessel/ROIs is/are being scanned so as to producecontrast-enhanced images of the highest possible resolution throughoutthe entirety of the ROI.

SUMMARY

An object of certain embodiments of this disclosure is to bring thebenefits of a consistent total volumetric flow rate to the situation ofdelivering complex, continuously varying, or optimized bolus shapes. Themore complicated the bolus profile, the more important it is to have aconsistent total volumetric flow rate to preserve the desired shape ofthe bolus into the central circulation.

As will become apparent in the following paragraphs, the embodimentsdescribed herein can be applied to a variety of prior art bolus deliveryor optimization techniques including those attempted by, for example,Mallinckrodt/Guerbet/Bae and Fleischmann et al. The provision of aconsistent volumetric flow rate over the delivery of the contrast andflushing fluid enables the bolus shape in the vessels and/or tissue ofinterest to be closer to what is expected or predicted and lessdependent on patient to patient variation as well as variations for thesame patient over time. This enables better scan timing and moreconsistent image quality. By reducing variation, it may be possible toreduce radiation and/or contrast media volumes as well.

In some non-limiting aspects of this disclosure, provided is a methodfor delivering a medical fluid. The method includes delivering a fluidvolume at a preselected total volumetric flowrate during a firstduration of a fluid delivery procedure, wherein the fluid volume iscomprised of a volumetric amount of a contrast agent and, optionally, avolumetric amount of a flush fluid. The method also includescontrollably varying the volumetric amount of the contrast agent in thefluid volume during the first duration of the fluid delivery procedureand controllably varying the volumetric amount of the flush fluid in thefluid volume during the first duration of the fluid delivery procedureso as to substantially maintain the preselected total volumetricflowrate throughout the first duration of the fluid delivery procedure.

In other non-limiting aspects of this disclosure, provided is a fluiddelivery system. The system includes a fluid administration deviceadapted to deliver a fluid volume, wherein the fluid volume comprises avolumetric amount of a contrast agent and, optionally, a volumetricamount of a flush fluid. The system also includes a controller incommunication with the fluid administration device, wherein thecontroller comprises a processor and a non-transitory machine-readablestorage medium. The non-transitory machine-readable storage mediumcomprises instructions that, when executed by the processor, enable thefluid administration device to: deliver the fluid volume at apreselected total volumetric flowrate during a first duration of a fluiddelivery procedure; controllably vary the volumetric amount of thecontrast agent in the fluid volume during the first duration of thefluid delivery procedure; and controllably vary the volumetric amount ofthe flush fluid in the fluid volume during the first duration so as tosubstantially maintain the preselected total volumetric flowratethroughout the first duration of the fluid delivery procedure.

Various aspects of the present disclosure may be further characterizedby one or more of the following clauses:

Clause 1. A method for delivering a medical fluid, comprising:delivering a fluid volume at a preselected total volumetric flowrateduring a first duration of a fluid delivery procedure, wherein the fluidvolume is comprised of a volumetric amount of a contrast agent and,optionally, a volumetric amount of a flush fluid; controllably varyingthe volumetric amount of the contrast agent in the fluid volume duringthe first duration of the fluid delivery procedure; and controllablyvarying the volumetric amount of the flush fluid in the fluid volumeduring the first duration of the fluid delivery procedure so as tosubstantially maintain the preselected total volumetric flowratethroughout the first duration of the fluid delivery procedure.

Clause 2. The method of clause 1, wherein the volumetric amount of thecontrast agent in the fluid volume is controllably decreased during thefirst duration of the fluid delivery procedure.

Clause 3. The method of either of clauses 1 or 2, wherein the volumetricamount of the flush fluid in the fluid volume is controllably increasedduring the first duration of the fluid delivery procedure.

Clause 4. The method of any of clauses 1-3, wherein the volumetricamount of the contrast agent in the fluid volume is continuouslydecreased during the first duration of the fluid delivery procedure.

Clause 5. The method of any of clauses 1-4, wherein the volumetricamount of the flush fluid in the fluid volume is continuously increasedduring the first duration of the fluid delivery procedure.

Clause 6. The method of any of clauses 1-5, wherein the volumetricamount of the contrast agent in the fluid volume is both controllablydecreased and controllably increased during the first duration of thefluid delivery procedure.

Clause 7. The method of any of clauses 1-6, wherein the volumetricamount of the flush fluid in the fluid volume is both controllablyincreased and controllably decreased during the first duration of thefluid delivery procedure.

Clause 8. The method of any of clauses 1-7, wherein the delivery of thecontrast agent is substantially completed during the first duration.

Clause 9. The method of any of clauses 1-8, wherein the volumetricamount of the contrast agent in the fluid volume is greater than zeroduring the first duration of the fluid delivery procedure

Clause 10. The method of any of clauses 1-9, further comprising:delivering a second fluid volume at a second preselected totalvolumetric flowrate during a second duration of the fluid deliveryprocedure, which is after the first duration, wherein the second fluidvolume is comprised of a second volumetric amount of the flush fluidand, optionally, a second volumetric amount of the contrast agent; andmaintaining the second preselected total volumetric flowrate throughoutthe second duration of the fluid delivery procedure.

Clause 11. The method of clause 10, wherein the second preselected totalvolumetric flowrate is substantially the same as the first preselectedtotal volumetric flowrate.

Clause 12. The method of either of clauses 10 or 11, wherein the secondfluid volume consists entirely of the flush fluid.

Clause 13. The method of any of clauses 10-12, wherein the secondduration of the fluid delivery procedure immediately follows the firstduration of the fluid delivery procedure.

Clause 14. The method of any of clauses 10-13, wherein the fluiddelivery procedure is substantially completed during the secondduration.

Clause 15. The method any of clauses 1-9, further comprising: deliveringa second fluid volume at a second preselected total volumetric flowrateduring a second duration, which is after the first duration, of thefluid delivery procedure, wherein the second fluid volume is comprisedof a second volumetric amount of the contrast agent and, optionally, asecond volumetric amount of the flush fluid; controllably varying thesecond volumetric amount of the contrast agent in the second fluidvolume during the second duration of the fluid delivery procedure; andcontrollably varying the second volumetric amount of the flush fluid inthe second fluid volume during the second duration of the fluid deliveryprocedure so as to substantially maintain the second preselected totalvolumetric flowrate throughout the second duration of the fluid deliveryprocedure.

Clause 16. The method of clause 15, wherein the second preselected totalvolumetric flowrate is substantially the same as the first preselectedtotal volumetric flowrate.

Clause 17. The method of either of clauses 15 or 16, wherein the secondduration of the fluid delivery procedure immediately follows the firstduration of the fluid delivery procedure.

Clause 18. A fluid delivery system, comprising: a fluid administrationdevice adapted to deliver a fluid volume, wherein the fluid volumecomprises a volumetric amount of a contrast agent and, optionally, avolumetric amount of a flush fluid; and a controller in communicationwith the fluid administration device, wherein the controller comprises aprocessor and a non-transitory machine-readable storage medium, whereinthe non-transitory machine-readable storage medium comprisesinstructions that, when executed by the processor, enable the fluidadministration device to: deliver the fluid volume at a preselectedtotal volumetric flowrate during a first duration of a fluid deliveryprocedure; controllably vary the volumetric amount of the contrast agentin the fluid volume during the first duration of the fluid deliveryprocedure; and controllably vary the volumetric amount of the flushfluid in the fluid volume during the first duration so as tosubstantially maintain the preselected total volumetric flowratethroughout the first duration of the fluid delivery procedure.

Clause 19. The fluid delivery system of clause 18, further comprising asource of the contrast agent and a source of the flush fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a Graphical User Interface (GUI) toset forth parameters for a plurality of phases for a two-syringeinjector also illustrated in FIG. 1 .

FIG. 2A is a graph of an injection profile of a contrast agent accordingto one embodiment of Bae et al.

FIG. 2B is a graph of the injection profile according to FIG. 2A inwhich a consistent total volumetric flowrate is maintained through theaddition of a flush fluid.

FIG. 3A is a graph of a two phase injection profile of a contrast agentaccording to one embodiment of Bae et al.

FIG. 3B is a graph of the injection profile according to FIG. 3A inwhich a consistent total volumetric flowrate is maintained through theaddition of a flush fluid.

FIG. 4A is a graph of an injection profile of a contrast agent accordingto one embodiment of Fleischmann et al.

FIG. 4B is a graph of the injection profile according to FIG. 4A inwhich a consistent total volumetric flowrate is maintained through theaddition of a flush fluid.

FIG. 4C is a graph of the injection profile according to FIG. 4B inwhich the initial flowrate is less than the total volumetric flowratethat is maintained through the addition of a flush fluid.

FIG. 4D is a graph of the injection profile according to FIG. 4A inwhich a consistent total volumetric flowrate that is higher than thecontrast flowrate is maintained through the addition of a flush fluid.

FIG. 5A is a graph of an injection profile of a contrast agent accordingto another embodiment of Fleischmann et al.

FIG. 5B is a graph of the injection profile according to FIG. 5A inwhich a consistent total volumetric flowrate is maintained through theaddition of a flush fluid.

FIG. 5C is a graph of the injection profile according to FIG. 5A inwhich a consistent total volumetric flowrate that is higher than thecontrast flowrate is maintained through the addition of a flush fluid.

FIG. 6 is a graph of a three phase injection profile according to oneembodiment of the Bayer P3T® protocol.

FIG. 7 is an illustration of the human body circulatory system andexemplary sizes of different portions thereof.

FIG. 8 is an illustration of a model of the venous system showing anexample of how the flowrates in different portions thereof can vary.

DETAILED DESCRIPTION

For purposes of the description hereinafter, spatial orientation termsshall relate to the embodiment as it is oriented in the drawing figures.However, it is to be understood that the various embodiments of thisdisclosure may assume alternative variations and step sequences, exceptwhere expressly specified to the contrary. It is also to be understoodthat the specific devices and processes illustrated in the attacheddrawings, and described in the following specification, are simplyexemplary. Hence, specific dimensions and other physical characteristicsrelated to the embodiments disclosed herein are not to be considered aslimiting.

As used in the specification, the singular form of “a”, “an”, and “the”include plural referents unless the context clearly dictates otherwise.

Unless otherwise indicated, all ranges or ratios disclosed herein are tobe understood to encompass any and all subranges or sub-ratios subsumedtherein. For example, a stated range or ratio of “1 to 10” should beconsidered to include any and all subranges between (and inclusive of)the minimum value of 1 and the maximum value of 10; that is, allsubranges or subratios beginning with a minimum value of 1 or more andending with a maximum value of 10 or less, such as but not limited to, 1to 6.1, 3.5 to 7.8, and 5.5 to 10.

All documents, such as but not limited to issued patents and patentapplications, referred to herein, and unless otherwise indicated, are tobe considered to be “incorporated by reference” in their entirety.

According to one aspect of this disclosure, a method for delivering amedical fluid is described. The medical fluid can include, but is notlimited to, a contrast agent, a flush fluid, and combinations thereof.The delivery of medical fluid can be part of an injection procedure inwhich the medical fluid is delivered to a patient, though thisdisclosure is not limited to fluid delivery only for this purpose.

The medical fluid can be delivered according to a “protocol.” As usedherein with respect to a fluid delivery procedure, the term “protocol”refers to a group of parameters such as flow rate, flow volume, deliveryduration, etc. that define the amount of fluid(s) to be delivered duringa fluid delivery procedure, such as to a patient during an injectionprocedure. Such parameters can change over the course of the procedure.As used herein, the term “phase” refers generally to a group ofparameters that define the amount of fluid(s) to be delivered during aperiod of time (or phase duration) that can be less than the totalduration of the fluid delivery procedure. The term “duration” is used torefer to any period of time of the fluid delivery procedure. A“duration” may be, in some instances, equivalent to a phase or to theentire delivery procedure, though it may also be used to refer to a morelimited period of time. Thus, the parameters of a phase or a durationprovide a description of the fluid delivery over a time instancecorresponding to the length of time of the phase or the duration. By wayof example, one parameter can be the initial total volumetric flow rate,which corresponds to the total volume of fluid per unit time beingdelivered at the onset of the phase. This initial total volumetricflowrate may be comprised of the fluid volume of more than one fluid,such as a first fluid and second fluid, that are being deliveredsimultaneously. For example, if, at the onset of a phase, a flowrate ofa first fluid is 5 mL/s and a flowrate of a second fluid is 2 mL/s, theinitial total volumetric flowrate would be 7 mL/s. Similarly, if thefluid delivery protocol requires only the first fluid to be delivered atthe onset of the phase, again at a flow rate of 5 mL/s, while none ofthe second fluid is delivered at the onset of the phase, the initialtotal volumetric flowrate would be 5 mL/s.

A fluid delivery protocol for a particular procedure can, for example,be described as uniphasic (a single phase), biphasic (two phases), ormultiphasic (two or more phases, but typically more than two phases).Multiphasic procedures also include procedures in which the parameters,such as flowrate, can change or vary continuously, semi-continuously,discretely, or in multiple steps over at least a portion of theprocedure. A continuously varying flowrate can be achieved through manyapproaches, including curvilinear approximations, piecewise linearapproximations, or a stepwise approximation.

As mentioned, the delivery of medical fluid described herein can be partof an injection procedure in which the medical fluid is delivered to apatient. An injection system 100 illustrated in FIG. 1 can be used withthe present disclosure. System 100 includes two fluid delivery sources(sometimes referred to as source “A” and source “B” herein; such assyringes) that are operable to introduce a first fluid and/or a secondfluid (for example, contrast agent, saline, etc.) to the patientindependently (for example, simultaneously, simultaneously in differentvolumetric flow proportion to each other, or sequentially or subsequentto each other (that is, A then B, or B then A)). Exemplary injectionsystems are those that are disclosed in: U.S. patent application Ser.No. 09/715,330, filed on Nov. 17, 2000, issued as U.S. Pat. No.6,643,537; U.S. patent application Ser. No. 09/982,518, filed on Oct.18, 2001, issued as U.S. Pat. No. 7,094,216; U.S. patent applicationSer. No. 10/825,866, filed on Apr. 16, 2004, issued as U.S. Pat. No.7,556,619; U.S. patent application Ser. No. 12/437,011, filed May 7,2009, issued as U.S. Pat. No. 8,337,456; U.S. patent application Ser.No. 12/476,513, filed Jun. 2, 2009, issued as U.S. Pat. No. 8,147,464;and U.S. patent application Ser. No. 11/004,670, filed on Dec. 3, 2004,issued as U.S. Pat. No. 8,540,698, the disclosures of each of which areincorporated herein by reference in their entireties.

In the embodiment of FIG. 1 , source A is in operative connection with apressurizing mechanism such as a drive member 110A, and source B is inoperative connection with a pressurizing mechanism such as a drivemember 110B. Injection system 100 includes a controller 200 in operativeconnection with injector system 100 that is operable to control theoperation of drive members 110A and 110B to control injection of fluid A(for example, a contrast agent) from source A and injection of fluid B(for example, a flush fluid such as saline) from source B, respectively.Controller 200 can, for example, include a user interface comprising adisplay 210. Controller 200 can also include a processor 220 (forexample, a digital microprocessor as known in the art) in operativeconnection with a memory 230. The memory 230 can be a non-transitorymachine-readable storage medium that includes program instructions thatcan be executed by the processor 220 to allow controller 200 to controlthe injection system 100 so as to perform the processes discussedherein, among other functions. Imaging system 300 can, for example, be aCT system, a MRI system, an ultrasound imaging system, a positronemission tomography (PET) system or another imaging system. Injectionsystem 100 can be in communicative connection with imaging system 300and one, a plurality, or all the components of injection system 100 andimaging system 300 can be integrated.

In some non-limiting embodiments, system 100 may include a singlecomputer, a server computer, a combination of computers, or any othercombination of hardware and/or software components. Controller 200 maybe considered to be an integral aspect of the injector 100 or a separatebut connected aspect of the overall imaging system 100. The individualunits or components of system 100 may be localized or, in someembodiments, distributed among any number of hardware devices, local orremote, preferably in communication with one another. Further, each unitmay itself be comprised of a distributed system, such as a series ofservers and/or computers networked together. In one non-limitingexample, certain components of system 100 may be incorporated into thesoftware and hardware associated with medical imaging equipment (e.g.,scanner and injector), such as the Certegra® Workstation product offeredby Bayer HealthCare LLC.

In several embodiments of the present disclosure, phase variables orparameters are populated within a phase programming mechanism (see FIG.1 for an embodiment of a user interface therefor that can, for example,be used with injector system 100) based on one or more parameters ofinterest, including, for example, but not limited to, contrast agentconcentration (for example, iodine concentration in the case of a CTprocedure), a patient parameter (for example, body weight, body massindex (BMI), height, gender, age, cardiac output, etc.) the type of scanbeing performed, and the type of catheter inserted into the patient forintravascular access. As discussed above, differences in dosingrequirements for different patients during imaging and other procedureshave been recognized. For example, U.S. Pat. Nos. 5,840,026 and6,385,483, assigned to the assignee of the present invention, thedisclosures of which are incorporated herein by reference, disclosedevices and methods to customize the injection to the patient usingpatient specific data derived before or during an injection. Likewise,U.S. Pat. No. 8,295,914, assigned to the assignee of the presentinvention, the disclosure of which is incorporated herein by reference,also discloses customization of injections to a patient using patientspecific data and sets forth a number of models to describe a timeenhancement output for a given input or protocol.

The clinical operator can control the injection system 100 either byentering volumes and flowrates manually into the fields provided on theuser interface, by selecting a pre-defined protocol, or by usingsoftware associated with the system, such as software in the form ofprogramming instructions residing in the non-transitory computerreadable medium of memory 230, to compute a protocol. The softwareassociated with the system 100 may compute an injection protocol for thedelivery of a fluid volume over time where the fluid volume includes atleast a volumetric amount of a first fluid, such as contrast agent,delivered at a flowrate that may vary over time and may be zero atcertain times, and a volumetric amount of a second fluid, such assaline, which also may be delivered at a flowrate that may vary overtime and may be zero at certain times.

The injection protocol can be determined by first determining theparameters (e.g., total volume, flowrate over time, etc.) for deliveringthe contrast agent, which collectively make up a contrast agentprotocol. The software can follow, for example, any of a variety ofknown models for determining the contrast agent protocol. These include,but are not limited to, contrast agent protocols that have beendeveloped to achieve a desired bolus profile or shape.

In one non-limiting embodiment, the delivery of contrast agent canfollow one of the contrast agent protocols described in U.S. Pat. Nos.6,055,985 and 6,635,030, both to Bae et al., the entire contents of eachof which are incorporated herein by reference. Bae et al. describe amethodology for determining a protocol for delivering a contrast agentto a patient which attempts to optimize the use of contrast agent toachieve an enhancement in excess of a preselected threshold and tomaintain that excess level of enhancement for a temporal duration thatis near optimal given the amount of contrast used.

For example, in U.S. Pat. No. 6,055,985, Bae et al. set forth variousramped, or multiphasic, or exponentially decaying, or steadilydecreasing injection rates. Bae et al. solve a set of differentialequations describing a simplified compartment model of a patient's bodyto render an exponentially decaying rate of contrast injection having aparticular decay coefficient, though it was contemplated that in thereal world, this exponentially decaying injection rate could beapproximated by a linear decay, or ramped decay, or even a multi-stepdecay. The particular decay coefficient calculated by Bae et al. isproportional to the cardiac output per body weight of the patient and isapproximated to be 0.01.

In one non-limiting embodiment of Bae et al., the contrast agentprotocol is determined by an initial delivery rate and an exponentialdecay coefficient. This is illustrated in FIG. 3 of U.S. Pat. No.6,055,985, a representation of which is provided as FIG. 2A herein. Theinitial delivery rate can be, for example, 2 mL/s. The total injectedvolume of contrast agent corresponds to the integrated sum of theinjection over the injection duration. The total injected volume ofcontrast agent can be, for example, 50 mL, 70 mL, or 90 mL. Bae et al.also disclose an exponential decay coefficient equal to Q/Vs, which isthe ratio of cardiac output (Q) to the systematic volume of distinctionof contrast agent, which itself is proportional to the cardiac outputper body weight (Vs). Bae et al. disclose and focus on decaycoefficients at or near 0.01, 0.02, and 0.03 and an injection durationof 120 seconds.

Bae et al. propose a contrast injection routine where an interval of theroutine begins at a preselected initial flowrate of contrast agent andthen the flowrate is controllably decreased during the routine atsubstantially an exponential rate having a decay coefficient thatapproximates the cardiac output per body weight that is typical of thepatient. Bae et al. also teach that functional patterns other than anexponential decay may be used to deliver the contrast agent, includingapproximating a short segment of an exponential curve by a linear orramped contrast agent protocol. Bae et al. provide an exemplary contrastagent protocol in which delivery of a contrast agent begins at apreselected initial injection flowrate and then the flowrate iscontrollably and continuously decreased, such as along a path ofexponential decay, until the desired volume of contrast has beendelivered and/or the desired injection duration has elapsed.

The techniques described by Bae et al. can be applied to the presentdisclosure as a method of delivering a volumetric amount of a contrastagent by controllably varying the flowrate of the contrast agent duringa least a portion of the injection procedure. For example, a contrastagent protocol for a particular patient can be determined according tothe techniques set forth by Bae et al. This contrast agent protocol canform part of the injection protocol, and particularly the portion of theinjection protocol that controls the delivery of a contrast agent.

In another non-limiting embodiment, the delivery of contrast agent canfollow one of the contrast agent protocols described in the article“Mathematical Analysis of Arterial Enhancement and Optimization of BolusGeometry for CT Angiography Using the Discrete Fourier Transform,”Journal of Computer Assisted Tomography, Volume 23(3), May/June 1999,pp. 474-484, by Fleischmann et al., the entire contents of which areincorporated by reference.

Fleischmann et al. describe a mathematical technique for the analysis ofan individual patient's contribution, referred to therein as the“patient function,” to the patient's time-attenuation response tointravenously injected contrast material. Fleischmann et al. assert thattheir technique can be used to predict the time-attenuation response toa given contrast agent bolus injection and calculate individually“optimized” injection parameters, which aim to achieve a uniformarterial opacification at a pre-defined level of enhancement for theentire scanning.

According to Fleischmann et al., a small bolus injection, a test bolusinjection, of contrast agent (16 ml of contrast at 4 ml/s) is made priorto a diagnostic scan. A dynamic enhancement scan is then made across avessel of interest. The resulting processed scan data (test scan) isinterpreted as the impulse response of the patient/contrast agentsystem. Fleischmann et al. derived the Fourier transform of the patienttransfer function by dividing the Fourier transform of the test scan bythe Fourier transform of the test injection. Assuming the system was alinear time invariant (LTI) system and that the desired output timedomain signal was known (a flat diagnostic scan at a predefinedenhancement level), Fleischmann et al. derived an input time signal bydividing the frequency domain representations of the desired output bythat of the patient transfer function. Because the method of Fleischmannet. al. computes input signals that are not realizable in reality as aresult of injection system limitations (for example, flow ratelimitations), one must truncate and approximate the computed continuoustime signal.

Fleischmann et al. also describe a technique to characterize, predict,and optimize enhancement using a set of mathematical relations. Therelations can be assembled into a notebook file of a commerciallyavailable computer program (Mathematica for Windows, enhanced version2.2.3; Wolfram Research, Champaign, Ill., U.S.A.). The Mathematicanotebook requires the input of (a) the test bolus, (b) the correspondingtest enhancement, (c) the parameters of an arbitrary standard bolus, andfinally (d) the desired “ideal” arterial enhancement.

To predict enhancement and to calculate an optimized injection bolus foran individual, the following steps were implemented by Fleischmann etal. Step 1: from the parameters (volume, flow rate) of the test bolusand the corresponding arterial time-attenuation response, the programcalculates the patient function in the Fourier space from the relationof a test bolus to a patient's corresponding aortic time-attenuationresponse, the test enhancement. The patient function plays the centralrole in predicting the individual enhancement response to a given bolus(e.g., a standard uniphasic injection), as well as in calculating the“ideal” injection parameters for a theoretically ideal (nearrectangular) enhancement curve. Step 2: once the patient function isknown, the standard enhancement to an arbitrary bolus, e.g., a 120 mlstandard bolus, can be predicted. Step 3: with the use of the patientfunction, calculate a theoretically “ideal” bolus, which should achievea near rectangular enhancement. Step 4: since the theoretically “idealbolus” contains “unreal” components in the time domain, likeoscillations, or negative flow rates, a fitting algorithm is introducedto approximate the ideal flow rates into a practically applicableoptimized biphasic bolus. The corresponding optimized enhancement can bepredicted as described in Step 2. Step 4 represents an independentlydeveloped fitting process in the time domain so as to produce a normalprofile.

A representation of an ideal bolus profile calculated according to themethods described by Fleischmann et al. is shown in FIG. 4A while anapproximation of this comparatively complex ideal bolus profile,referred to as a normal bolus profile, is shown in FIG. 5A. This normalprofile is manifested as a relatively large magnitude rectangular bolusof contrast in the first phase of an injection procedure followed by acomparatively smaller, long rectangular contrast bolus in the secondphase of the procedure.

The techniques described by Fleischmann et al. can be applied to thepresent disclosure as a method of delivering a volumetric amount of acontrast agent by controllably varying the flowrate of the contrastagent during a least a portion of the injection procedure. For example,a contrast agent protocol for a particular patient can be determinedaccording to the process set forth by Fleischmann et al. This contrastagent protocol can form part of the injection protocol, and particularlythe portion of the injection protocol that controls the delivery of acontrast agent.

The above described contrast agent protocols are intended to beexemplary only. One of skill in the art would recognize, upon readingthe present disclosure, that a fluid delivery procedure may employ othercontrast agent protocols, including other protocols in which theflowrate of contrast varies over time, such as contrast agent protocolsin which the delivery of contrast continuously varies over the course ofadministering the contrast agent.

As mentioned, the fluid volume delivered according to an injectionprotocol of the present disclosure can include, in addition to avolumetric amount of a contrast agent, which can be delivered accordingto the contrast agent protocols discussed above, a volumetric amount ofa flush fluid, such as saline. Like with the delivery of contrast, thevolumetric amount of the flush fluid may be delivered at a flowrate thatvaries throughout the injection procedure.

In one aspect of this disclosure, the parameters for the delivery of theflush fluid are selected so as to substantially maintain a consistenttotal volumetric flowrate throughout at least some duration of the fluiddelivery procedure. For example, a substantially consistent totalvolumetric flowrate can be maintained throughout the entirety of atleast one phase of the fluid delivery procedure. By way of anotherexample, a substantially consistent total volumetric flowrate can bemaintained throughout at least that portion of the procedure wherecontrast agent is being delivered. In yet another example, asubstantially consistent total volumetric flowrate can be maintainedthroughout the entirety of the fluid delivery procedure, such as acrossall phases of a multiphasic procedure.

The total volumetric flowrate value that is maintained can be apreselected value that is selected in advance of initiating the fluiddelivery procedure or a phase thereof. In one non-limiting embodiment,the total volumetric flowrate that is maintained is substantially thesame as the initial total volumetric flowrate at the onset of the fluiddelivery procedure or a phase thereof. In another non-limitingembodiment, the total volumetric flowrate that is maintained is higherthan the initial total volumetric flowrate at the onset of the fluiddelivery procedure or a phase thereof. In this embodiment, the initialtotal volumetric flowrate is increased, such as through a gradual rampup, so that the total flowrate reaches the preselected total volumetricflowrate. Use of this ramp up period can help avoid the whip or shock toa patient's venous system that could come through the suddenadministration of a high fluid volume. In yet another non-limitingembodiment, the initial total volumetric flowrate at the onset of thefluid delivery procedure or a phase thereof is greater than thepreselected total volumetric flowrate. The initial total volumetricflowrate is then decreased so that the total flowrate reaches thepreselected total volumetric flowrate. In one non-limiting embodiment,the total volumetric flowrate that is maintained may be equal to themaximum flowrate of contrast agent achieved during the fluid deliveryprocedure. In another non-limiting embodiment, the total volumetricflowrate that is maintained may be greater than the maximum flowrate ofcontrast agent achieved during the fluid delivery procedure. Regardlessof the relationship between the initial total volumetric flowrate andthe preselected total volumetric flowrate that is maintained, the totalvolumetric flowrate can be gradually ramped down toward the end of thefluid delivery procedure or phase thereof to, for example, avoidpressure bleed off. The flow may dither, oscillate, or vary at afrequency high enough that it is smoothed out by the fluid vessel volumeand flows in the body, effectively providing a sufficiently constanttotal volumetric flow.

For purposes of this disclosure, a “substantially consistent totalvolumetric flowrate” means that the fluid volume per unit time remainsconstant over the timeframes and intervening fluid volumes relevant tothe contrast reaching the regions of interest within a target margin ofvariation over the timeframe of interest in the imaging study. Anexemplary target may be a margin of variation of less than 20% byvolume, such as less than 10% or less than 5% by volume. The specificnumeric value may depend upon the injection flow rate in relation to thepatient's peripheral vessel flowrates as discussed above in relation toFIGS. 7 and 8 . As discussed above, the fluid volume can include morethan one fluid. For example, the fluid volume can include a volumetricamount of a contrast agent and a volumetric amount of a flush fluid suchas saline. Two contrasts of different concentrations may be used.Alternatively, three or more fluids may be used, for example twocontrasts with properties that may be distinguished by the imagingsystem in use and a flush fluid such as saline.

If the flowrate of contrast agent varies during the fluid deliveryprocedure or a phase thereof, as it does in the contrast agent protocolsdiscussed above, maintaining a substantially consistent total volumetricflowrate of a fluid volume that includes both a contrast agent and aflush fluid during the procedure and/or phase requires varying the rateat which the flush fluid is delivered in a manner that is complementaryto the variation in the flow of contrast. For example, if the contrastdelivery protocol employs an exponentially decaying contrast flowrate,as illustrated in FIGS. 2A-2B, the flow rate of flush fluid wouldcontinually increase to maintain a substantially consistent totalvolumetric flowrate. This is illustrated in FIG. 2B, where thecontinually decreasing flowrate of contrast agent (FR_(c)) is counteredwith a continually increasing flow of flush fluid so that the totalvolumetric flowrate (FR_(tot)) of the fluid volume, where the fluidvolume is made up of contrast and flush fluid, remains substantiallyconsistent over the entire portion of the procedure depicted in FIG. 2B.In this example, the total volumetric flowrate (FR_(tot)) that ismaintained is substantially the same as the initial total volumetricflowrate at the onset of the fluid delivery procedure (FR_(int)) which,in this example, consists entirely of contrast. The volume of contrastdelivered is represented by the area “C” while the volume of flush fluiddelivered is represented by the area “F.”

FIGS. 3A-3B provides another example of how the flow of flush fluid canbe delivered in a two phase injection procedure which employs anexponentially decaying contrast flowrate in the first phase (“PHASE1”)followed by a second phase (“PHASE2”) consisting of only flush fluid. Inthe first phase, the total volumetric flowrate (FR_(tot)) throughout thephase is held equal to the initial total volumetric flowrate at theonset of the phase (FR_(int)) which, in this example, consists entirelyof contrast. As the volumetric flowrate of the contrast agent (FR_(c))decays exponentially throughout the first phase, as shown in FIG. 3B, aflush fluid is added at a rate that increases at the same rate that theflowrate of contrast is experiencing its decay. As shown in FIG. 3B, theresult is a first phase in which the total volumetric flowrate(FR_(tot)) remains relatively consistent while the contrast flowrate(FR_(c)) is decaying from its initial rate, and the administration offlush fluid (e.g., saline) is increasing from zero. This is followed bya second phase in which only flush fluid is delivered at the same totalvolumetric flowrate (FR_(tot)). The illustration of FIG. 3B representsan improvement upon the bolus profile of FIG. 3A (which, as discussedabove, represents the OptiBolus profile according toMallinckrodt/Guerbet/Bae et al.). The fluid delivery procedure depictedin FIG. 3B adopts the consistent total volumetric flow approach of thepresent disclosure, which helps preserve the contrast bolus shape as thebolus traverses the peripheral vasculature. The volume of contrastdelivered is represented by the area “C” while the volume of flush fluiddelivered is represented by the area “F.”

By way of another example, if the delivery of contrast follows aprotocol in which the flow rate of contrast agent both increases anddecreases during the injection procedure, flush fluid can be added at avolumetric flowrate that is complementary to the time varying rate atwhich the contrast agent is being simultaneously delivered. Forinstance, FIG. 4A illustrates an ideal contrast agent protocol developedunder the method described by Fleischmann et al. As alluded topreviously, the contrast agent protocol shown in FIG. 4A dictates thatthe contrast be administered to the patient according to a time-varyingcontrast flowrate (FR_(c)), and thus results in the contrast beinginjected at a continuously or semi-continuously varying volumetricflowrate over the duration of the contrast injection portion of theprocedure. If such a contrast agent protocol is used, a flush fluid canbe added over the course of the contrast injection so as to achieve aconsistent total volumetric flowrate (FR_(tot)) and thus consistentdelivery of the fluid volume, including the contrast agent, to thecentral circulation over the entire contrast injection procedure. Thisis illustrated in FIG. 4B. In this example, the flowrate of contrastagent (FR_(c)) and flush fluid both continuously vary, both upward anddownward, during the contrast injection procedure so as to maintain asubstantially consistent total volumetric flowrate (FR_(tot)). In thisexample, the total volumetric flowrate (FR_(tot)) is held equal to theinitial total volumetric flowrate at the onset of the procedure(FR_(int)) and is preferably, but not necessarily, equal to or greaterthan the maximum flowrate of the contrast agent during the procedure. Inthis example, the initial total volumetric flowrate at the onset of thephase (FR_(int)) includes both a volumetric amount of contrast agent (C)and a volumetric amount of flush fluid (F). The illustration of FIG. 4Brepresents an improvement upon the bolus profile of FIG. 4A (which, asdiscussed above, represents the ideal profile according to Fleischmannet al.). The fluid delivery procedure depicted in FIG. 4B adopts theconsistent total volumetric flow approach of the present disclosure,which helps preserve the contrast bolus shape as the bolus traverses theperipheral vasculature. The volume of contrast delivered is representedby the area “C” while the volume of flush fluid delivered is representedby the area “F.”

FIG. 4C represents a variation of FIG. 4B in which the total volumetricflowrate that is maintained (FR_(tot)) is higher than the initial totalvolumetric flowrate (FR_(int)) at the onset of the fluid deliveryprocedure. In this embodiment, the initial total volumetric flowrate(FR_(int)), which consists entirely of contrast agent, is increasedthrough a gradual ramp up so that the total flowrate reaches thepreselected total volumetric flowrate (FR_(tot)) which is thenmaintained. In this embodiment, flush fluid is added only after thetotal volumetric flowrate (FR_(tot)) is reached. The volume of contrastdelivered is represented by the area “C” while the volume of flush fluiddelivered is represented by the area “F.”

Another example is shown in FIGS. 5A-5B. In FIGS. 5A-5B, a first phase(“PHASE1”) includes contrast agent administered as a relatively largerectangular bolus and a second phase (“PHASE2”) in which contrast isadministered as a smaller and longer bolus. The administration ofcontrast in this example is modeled after the normal Fleischmann et al.profile, discussed above. In the second phase (“PHASE2”) of FIG. 5B,however, unlike the smaller contrast-only second phase shown in FIG. 5A,flush fluid is added to the injection so that the resulting admixture ofcontrast and flush fluid is delivered at the same total volumetricflowrate (FR_(tot)) as provided in the first contrast-only phase. Thisis followed by a third phase (“PHASE3”) in which only flush fluid isinjected at the same total volumetric flowrate (FR_(tot)), as shown inFIG. 5B. The illustration of FIG. 5B thus represents an optimizedversion of the normal bolus profile developed by Fleischmann et al., onein which a consistent total volumetric flow rate is used throughout thefirst contrast-only phase, the second admixture phase, and the thirdflush fluid-only phase. In this embodiment, the flowrate of the contrastagent is constant across each phase, and thus does not vary, across anyparticular phase of the procedure. The volume of contrast delivered isrepresented by the area “C” while the volume of flush fluid delivered isrepresented by the area “F.”

A comparison of FIG. 5B and FIG. 6 reveals that this optimized versionof the normal Fleischmann et al. bolus profile yields a result similarin appearance to what can be accomplished using the P3T® softwareoffered by Bayer, though the injection protocol or parameters ofinjection used in the Fleischmann et al. bolus are derived using adistinctly different methodology than in the P3T® software offered byBayer.

In some situations or imaging studies, the flowrate of the contrastagent may be low compared to the flow of the blood in the patient's limbcirculation, for example 0.1 ml/s of contrast agent. In this situation,it may be desirable to provide a total volumetric flowrate that isgreater than the contrast flowrate over at least the entire period oftime the contrast agent is being delivered, as shown in FIG. 4D and FIG.5C, which are variations of FIG. 4C and FIG. 5B, respectively. For anormal adult, this desirable total volumetric flowrate may be, forexample, on the order of 0.5 ml/s to 1 ml/s. For other body sizes, thismay be scaled accordingly. By maintaining a total volumetric flowrate ofthis magnitude, the contrast agent and the flush fluid are movedexpeditiously through the patient's veins into the central circulation.Without this additional flow, the veins may initially expand to hold theinjected fluid volume and thus delay the transmission of the contrastagent to the central circulation and/or significantly distort the bolusshape or profile. Alternatively, if the veins are already fullydistended, the veins may have large enough volumes that the normalvenous flow is slow and injections at very low flowrates will result ina significant delay in the bolus arrival to the central circulation. Byproviding a higher total volumetric flowrate, the contrast agent andflush fluid are more quickly and predictably transmitted to the centralcirculation.

As discussed above, the variation of the flowrate of the flush fluid canbe chosen so as to substantially maintain a preselected total volumetricflowrate even as the flowrate of the contrast agent varies. The protocolfor delivering the flush fluid, including the flush fluid flowrate overtime, can be determined by first determining the flow volume of thecontrast agent at various points during the fluid delivery procedure ora portion thereof, as described above, and then subtracting the flowrateof the contrast agent from the total volumetric flowrate to ascertainthe flow rate of the flush fluid needed at each of these points to reachthe total volumetric flowrate. The calculated flowrate of the flushfluid can be used by controller 200 to control delivery of the flushfluid. Alternative means of determining the protocol for delivering theflush fluid are also available, including an algorithmic approach inwhich a protocol for delivering the flush fluid is developed based onthe contrast agent protocol and the value of the total volumetricflowrate at each point in time, as would be understood by a person ofskill in the art upon reading the present disclosure.

Although the present invention has been described in detail inconnection with the above embodiments and/or examples, it should beunderstood that such detail is illustrative and not restrictive, andthat those skilled in the art can make variations without departing fromthe invention. The scope of the invention is indicated by the followingclaims rather than by the foregoing description. All changes andvariations that come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

The invention claimed is:
 1. A method for delivering a medical fluid,comprising: delivering a fluid volume at a preselected total volumetricflowrate during a first duration of a fluid delivery procedure, whereinthe fluid volume is comprised of a volumetric amount of a contrast agentand a volumetric amount of a flush fluid; controllably varying thevolumetric amount of the contrast agent in the fluid volume during thefirst duration of the fluid delivery procedure, wherein the volumetricamount of the contrast agent is controllably decreased at anexponentially decaying rate during at least a portion of the firstduration; and controllably varying the volumetric amount of the flushfluid in the fluid volume while the volumetric amount of the contrastagent is being controllably decreased so as to substantially maintainthe preselected total volumetric flowrate throughout the first durationof the fluid delivery procedure, wherein the delivery of the contrastagent is substantially completed during the first duration.
 2. Themethod of claim 1, wherein the method comprises delivering the medicalfluid to a patient, and wherein the exponentially decaying rate decaysaccording to a decay coefficient that is proportional to a cardiacoutput per body weight of the patient.
 3. The method of claim 1, whereinthe exponentially decaying rate decays according to a decay coefficientthat is approximately 0.01 to 0.03.
 4. The method of claim 1, whereinthe volumetric amount of the contrast agent in the fluid volume isgreater than zero during the first duration of the fluid deliveryprocedure.
 5. The method of claim 1, wherein an initial total volumetricflowrate at an onset of the first duration consists entirely ofcontrast.
 6. The method of claim 1, further comprising: delivering asecond fluid volume at a second preselected total volumetric flowrateduring a second duration of the fluid delivery procedure, which is afterthe first duration, wherein the second fluid volume comprises a secondvolumetric amount of the flush fluid; and maintaining the secondpreselected total volumetric flowrate throughout the second duration ofthe fluid delivery procedure.
 7. The method of claim 6, wherein thesecond preselected total volumetric flowrate is substantially the sameas the first preselected total volumetric flowrate.
 8. The method ofclaim 6, wherein the second fluid volume consists entirely of the flushfluid.
 9. The method of claim 6, wherein the second duration of thefluid delivery procedure immediately follows the first duration of thefluid delivery procedure.
 10. The method of claim 6, wherein the fluiddelivery procedure is substantially completed during the secondduration.
 11. The method of claim 1, further comprising: delivering asecond fluid volume at a second preselected total volumetric flowrateduring a second duration, which is after the first duration of the fluiddelivery procedure, wherein the second fluid volume is comprised of asecond volumetric amount of the contrast and a second volumetric amountof the flush fluid; controllably varying the second volumetric amount ofthe contrast agent in the second fluid volume during the second durationof the fluid delivery procedure; and controllably varying the secondvolumetric amount of the flush fluid in the second fluid volume duringthe second duration of the fluid delivery procedure so as tosubstantially maintain the second preselected total volumetric flowratethroughout the second duration of the fluid delivery procedure.
 12. Themethod of claim 11, wherein the second preselected total volumetricflowrate is substantially the same as the first preselected totalvolumetric flowrate.
 13. The method of claim 11, wherein the secondduration of the fluid delivery procedure immediately follows the firstduration of the fluid delivery procedure.
 14. A fluid delivery system,comprising: a fluid administration device adapted to deliver a fluidvolume, wherein the fluid volume comprises a volumetric amount of acontrast agent and a volumetric amount of a flush fluid; and acontroller in communication with the fluid administration device,wherein the controller comprises a processor and a non-transitorymachine-readable storage medium, wherein the non-transitorymachine-readable storage medium comprises instructions that, whenexecuted by the processor, enable the fluid administration device to:deliver the fluid volume at a preselected total volumetric flowrateduring a first duration of a fluid delivery procedure; controllably varythe volumetric amount of the contrast agent in the fluid volume duringthe first duration of the fluid delivery procedure, wherein thevolumetric amount of the contrast agent is controllably decreased at anexponentially decaying rate during at least a portion of the firstduration; and controllably vary the volumetric amount of the flush fluidin the fluid volume while the volumetric amount of the contrast agent isbeing controllably decreased so as to substantially maintain thepreselected total volumetric flowrate throughout the first duration ofthe fluid delivery procedure, wherein the delivery of the contrast agentis substantially completed during the first duration.
 15. The fluiddelivery system of claim 14, further comprising a source of the contrastagent and a source of the flush fluid.